The invention relates to a simulator apparatus with at least two degrees of freedom of movement for an instrument that has an elongated shaft comprising a holding device for the instrument, the holding device being designed such that the instrument has at least a first degree of freedom of a swivelling movement about a first swivel axis and at least a second degree of freedom of swivelling movement about a second swivel axis, running perpendicular to the first swivel axis.
Such a simulator apparatus is known for example from U.S. Pat. No. 6,024,576.
In general, such a simulator apparatus is used as interface between an operator and an instrument in simulators. A specific use, to which the following description relates without limiting the present invention thereto, is the integration of a simulator apparatus mentioned at the beginning in a simulator for simulating a minimally invasive surgical intervention in a human or animal body.
The term “instrument” is to be understood generally in the sense of the present invention, and in the case of a medical simulation, it can be an endoscope, a tool such as scissors, forceps, a dissector, clamp applicator etc.
In recent years, minimally invasive surgery has gained clearly in importance by comparison with open surgery. In minimally invasive surgery, a viewing system, for example an endoscope, and one or more instruments such as forceps, scissors, HF instruments, clamp applicators, etc. are introduced into the body by minimal incisions. The minimally invasive surgical operation is carried out with video assistance with the aid of the abovementioned instruments in combination with peripheral devices.
At present, minimally invasive surgery is used, for example, for removing a gall bladder, the appendix and for handling herniotomies. Further fields of use are being opened up.
However, “minimally invasive” surgery covers as a term not only surgical interventions, but also interventions such as, for example, the introduction of substances into the body, or biopsies where use is made of the minimally invasive technique.
By contrast with open surgery, the advantage of the minimally invasive technique resides in the mode of procedure, which spares the patient and entails less surgical trauma, shorter times of stay in hospitals and a shorter incapability for work.
By contrast with open surgery, however, the handling of the instruments during a surgical intervention is substantially more complicated, firstly because the freedom of movement of the instrument inserted through the incision is restricted because of the only small incision, and secondly because the surgeon does not himself have a clear dimensional view of the working tip of the instrument located in the body, nor of the operating site, but instead only a two-dimensional visual monitoring is possible via the video monitor. It goes without saying that the coordination of the guidance and operation of the instrument or instruments are thereby rendered more difficult.
There is thus a greater need for training in the new techniques of minimally invasive surgery. Various alternatives currently exist for training in surgical procedures of minimally invasive surgery.
One alternative consists in carrying out training operations in vivo on animals, specifically on pigs. However, such training is cost intensive, time consuming to prepare and, moreover, ethically dubious.
In the case of a further alternative, physicians are trained on in vitro organs in a training box into which the instruments can be appropriately introduced. The organs arranged in the training box are certainly biological organs, but training in the case of this alternative is likewise time consuming to prepare and cannot be regarded as realistic.
Finally, training in minimal invasive surgery is currently being carried out on model organs or training objects in a training box. However, such model organs are not sufficiently realistic for training for an entire operation. Moreover, the preparation of the model organs and training objects requires a not inconsiderable preparatory outlay, since the models are for the most part destroyed during the operation and initially require to be prepared again for further training sessions.
Because of the disadvantages of the training systems used to date, there was already a need very early for so called virtual simulators that can be used to overcome the disadvantages of the previous training systems.
The actual operating site is generated exclusively via a computer in the case of virtual simulation. Realistic simulation requires a model database that fixes the geometric shapes and physical properties of the tissues, organs and vessels, as well as the geometry and kinematics of the instrument or instruments. In the journal “Biomedical Journal”, Volume No. 51, April 1998, U. Kühnapfel describes a “Virtual-Reality-Trainingssystem für die Laparoskopie” [“Virtual reality laparoscopy training system”] that has an input box which exhibits from the outside the customary instrument grips and a virtual endoscope. In the housing, the minimally invasive instruments are guided in a mechanical guide system that further permits the detection of the deflection of the instruments and actuators. In addition, various foot switches are present that can be used to activate surgical and general functions. Via angle encoders, for example, a PC-based sensor data acquisition process measures the positions of the joints of the operating instruments and transmits these continuously to a graphics workstation. A “virtual” image of the endoscope view is calculated there from in real time. The consistency of the tissue to be treated is fed back to the operator realistically as force feedback by inherently calculated “virtual” reactive forces between organs and instruments.
Consequently, in the case of virtual simulation of minimally invasive interventions, no use is made of physically present organs—instead the spatial and physiological structures of such organs are present as data in a computer. The simulator apparatus mentioned at the beginning in this case forms the interface between the operator and the instrument to be handled and the simulation computer system. The operator to be trained handles the instrument accommodated in the mechatronic simulator apparatus, the data stored in the computer, for the spatial and physiological structure of the virtual organ being transmitted as force feedback by the simulator apparatus to the instrument while the latter is being handled, as a result of which the operator is afforded a realistic feel.
The previous developments in this field have concentrated primarily on the creation of the simulation software, while so far available holding systems capable of localization have been used as mechatronic simulator apparatus. In the interests of realistic simulation, the simulator apparatus should take account of all degrees of freedom that are present for a minimally invasive surgical instrument, specifically a tilting of the instrument about the surface of the body, a movement in the direction of the shaft and a rotary movement about the longitudinal axis of the shaft. However, a problem in this is the mechanical implementation of these many degrees of freedom in the holding device of the simulator apparatus for the instrument.
For example, the simulator apparatus known from U.S. Pat. No. 6,024,576 cited above comprises a complicated mechanical lever system whose disadvantage resides particularly in the fact that the simulator apparatus is very large overall. It is therefore impossible using such a simulator apparatus for two or more apparatuses to bring a plurality of instruments so close together that the instrument tips can touch. Because of the many levers used in this known simulator apparatus, undesirable moments of inertia and torques occur when this simulator apparatus is being used and must be compensated in a complicated way in order to permit a realistic force feedback.
WO 96/30885 discloses a virtual surgical system for simulating surgical interventions on the basis of image data. It is possible thereby to simulate a surgical procedure by using the image data of a patient, it being possible to simulate the instruments used by a surgeon in carrying out an actual procedure. This known apparatus makes use as input apparatus of a mouse, a three-dimensional mouse, a joystick or a seven-dimensional joystick. The joystick provided in the known apparatus is designed in the form of a lever at whose lower end a ball is arranged that can be rotated in various directions of solid angle in a ball cup. However, a mouse or a joystick does not correspond to the application of an actual surgical instrument.
Further, EP-0 970 662 A1 discloses a simulator apparatus for simulating the insertion of a catheter into blood vessels. The simulated catheter has only degrees of freedom of rotation about the longitudinal axis of the catheter, and of translatory movement in the direction of the longitudinal axis of the catheter. Provided for the purpose of achieving a force feedback is a gear arrangement that has, inter alia, a differential gear which, however, is arranged with reference to the longitudinal central axis of the catheter in a fashion laterally apart and aside from the latter, and which is connected to the catheter via various stands and holding devices.
It is therefore the object of the invention to specify a simulator apparatus of the type mentioned at the beginning that has a compact design and mechanics of low torque.